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J.Zool.6l:2533-2539. defense mechanism and it has been assumed that feu' MnosovsKy, N., RNn PnovaNCuR, J. 1992. Sex ratio of hatchling predators other than killer whales (Orcinus orca) and lar_ee loggerhead sea tr-rfiles : data and estimates from a 5 -year str,rdy. Can. sharks actively prey upon adult sea turtles (Cornelius. J. Zool.70:530-538. 1986). The ability of American crocodiles (Crococlt'lu.s MnosovsKy, N.,, Rr.ro YNrEvn. C.L. 1980. Temperature dependence of acuttts) and saltwater crocodiles (C. porosus) to tolerate it sexual differentiation in sea tuftles: implications for conservation marine habitat (Mazotti r practices. Biol. Conserv . 18:21I -280. and Dunson, 1984; Taplin. 1988 MnosovsKy, N., DurroN, P.H., AND WHnuone, C.P. 1984a. Sex ratios provides these predators the opportunity to exploit rnarine of two species of sea turtle nesting in Sr"rriname. Can. J. Zool. prey such as sea turtles. However, published accounts t-rf 62:2221-2239. crocodile predation on or consumption of sea turtles itre feu 586 CHEr-olunN CoNSERVATToN AND BtoLocy, Volume 2, Nantber 4 - I997 (Allen, 197 4: Limpus et al., 1983 ; Pdrez Higareda et al., month observation period, a total of I 1 turtle carcasses were 1989; Hirth et al., 1993). found of which 9 were attributed to crocodile predation. Turtles of the genus Lepidochelys sometimes display a Because carcasses were always found on the beach we as- unique nesting behavior tetmed arribada (Spanish for "ar- sumed that the crocodile's attack occuffed on land. However, dval") in which thousands of females synchronously ascend a we can not rule out the possibility that the crocodile killed the single beach on one or a few successive nights (or days) to lay turtles at sea and the carcasses washed up on shore. The their eggs (Richard and Hughes, 1912; Cornelius, 1986). observation of a crocodile stalking a nesting turtle suggests that Arribadas typically occur once a month during the nesting crocodiles capture and kill turtles in nearshore waters. The season, while some solitary nesters may nest every night. second author observed a solitary turtle emerge on the beach in Pritchard ( 1969) and Eckrich and Owens ( 1995) hypothesized the late afternoon to lay eggs, while a large crocodile (ca. 3 m that arribada behavior evolved as a predator satiation mecha- TL) remained offshore (ca. 25 m) observing the turtle from nism in which the probability of individual predation is re- shallow water (< 1 m). When the tuftle completed nesting and duced. began her return to the water, the crocodile moved towards her, During the arribado season between July and November remaining concealed in the water. As the turtle reached the of 1990, we observed and recorded evidence of predatory water's edge, two volunteers came running down the beach, activity of the American crocodile (C. acutus) upon olive sending the crocodile offto deeper water and abandoning what ridley sea turtles (L. olivacea) during the turtle's nesting season appeared to be an impending attack on the turtle. at Playa Nancite, Santa Rosa National Park, Gulf of Papagayo, Predation on adult turtles was charactenzed by frontal Pacific coast of Costa Rica. We documented: 1) the date attacks, with usually one fresh tuftle carcass on the beach at a crocodiles, their tracks, and depredated turtle carcasses ap- time. Frontal attacks by C.acutus and Morelet's crocodile (C. peared, 2) direction of crocodile tracks (leaving from or moreleli) on prey have been reported in Mexico (Casas Andreu retuming to the estualy), and 3) condition of turtle carcasses. and Guzmftn Arroyo, l9l0;Pdrez Higareda et al., 1989). In American crocodiles inhabit the estuary behind the turtle Papua New Guinea, the occuffence of a frontal attack by a nesting beach at Playa Nancite. The ca. 1.1 km stretch of beach crocodile (presumably C. porosus; species not mentioned) on is bordered by two rocky headlands, isolating the estuary, a leatherback sea turtle (Dennochelys coriacea) has been therefore making the beach the only access to the ocean for the documented (Hinh et al., 1993).